I have a stock 05 STI and my main question is whether or not I should go with a turbo-back exhaust or cat-back first.. i plan on getting the k&n typhoon intake soon and an ACT clutch kit as well then possibly a cobb accessport and i was thinking of the invidia v3 downpipe... unless the turbo back exhaust comes with the downpipe which would make sense.. im sorta new to all this. So which type of exhaust would be best for my car and any suggestions on which brand to go with? Im not looking for the ricer slanted exhaust however. Any advice? Thanks!

Honestly i would say turboback...skip the intake, at least the k&n...get an sf short ram intake if you just want the sound. It also helps slightly if used with the ap maps. But an intake is for the most part not necessary as an early mod. Tends to cause af ratio probs unless tuned for...and can be tough to tune for depending on brand. As far as brand of exhaust...well i would get pn you tube and listen to every kind you can there are lots of options out there if you want to stay away from the can style you may want to look at the Cobb turboback. Its nice but a little expensive.

Well I was going for the intake for the performance aspect, and i was told if i bought the CAI i would need to buy a mass air flow sensor to go with it? Would that fix the af ratio problems? I was planning to get all those mods then get the ap maps to bring it all together.. and with a turbo back exhaust I dont need to buy a downpipe right?

The CAI will hurt your performance without a tune, even with the big MAF. The only difference between the cat back and turbo back is that the turbo back has a down pipe. If your getting a turbo back you need a stage 2 tune anyway so you might as well get the intake to and do it all at once. If your going OTS with the AP I'd check cobbs notes first because I don't think they make a map for the k&n.

What intakes do the cobb ap have maps for? and would it be better to buy a cat back and get a downpipe or get the turbo back with the dp it comes with... like which way would get me more power? if that makes any sense at all...

OTS= off the shelf, I'm not sure what intakes they have maps for. I know the Cobb intake for sure the AVO short ram and I think AEM. Best thing is to check the web site or call them. For your exhaust it's up to you a lot of people get the DP they want and then find a cat back that has the sound their looking for. Either way the power should be about the same, the only thing that's gonna change the HP is if you get a catted DP or cat less, going cat less will net you a couple HP...... My only advice on brand is stay away from eBay junk.

What intakes do the cobb ap have maps for? and would it be better to buy a cat back and get a downpipe or get the turbo back with the dp it comes with... like which way would get me more power? if that makes any sense at all...

It tunes for all of them, when you get a custom tune (which you should be doing anyways). Skip the free maps from Cobb.

For intakes, I have NEVER seen one installed that didn't throw A/F ratio off, even though they ALL advertise they don't. As much as 25%, usually in the midrange! The amount of knock correction your car does to make up for that sickly lean condition will hurt your performance, and the "need new maf" statement is just bogus. The only reason you would ever need a different maf "housing" is if your maxing out your current maf, (5v), which is usually around 450whp. I currently never recommend anything beyond a drop in filter (except maybe on 08+'s), because it's simply not worth it. For the exhaust, a cat-back is more about sound, I can claim from experience the gains from a cat-back are very small. The downpipe is where you get your gains, lots of extremely hot gas needing to get past that turbo. By the time it gets to your cat back it has cooled so much you could argue that going to what most use (3") is actually too big, because the velocity of gases slow down so much. I would suggest what most the major tuners suggest which is, drop-in filter, 3" downpipe, and tune and call it a day. In the end you will have less money in it, and a much better running car.

I've seen it with my own eyes on more then one forced induction car. Even the testing in your link shows evidence of this, out of the two CAI's tested only one didn't make the car run lean. I never said anything about SRI's "even tho most SRI's I wouldn't trust without a tune either" so throw that intake out and 50% of the tested intakes hurt the performance of the car without a tune. That's enough for me not to just throw an intake on and hope it doesn't lean me out.

Thanks this is all awesome advice! and i am for sure wanting a custom tune the only problem is im here in souther new mexico and no one around here has any legit shops so im thinking ive got to head over to phoenix for a legit shop. and as far as exhausts go im leaning more towards the cat back and my choice of DP but ive heard there are a few issues with the invidia DP fitting with some exhausts, is this true? Im looking at either a perrin exhaust, AMS exhaust, or blitz nur spec exhaust. unless there are some others that sound better that i havent come across yet?

The fact that you think all forced induction cars are the same is one issue.

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Originally Posted by black beast2

Even the testing in your link shows evidence of this, out of the two CAI's tested only one didn't make the car run lean. I never said anything about SRI's "even tho most SRI's I wouldn't trust without a tune either" so throw that intake out and 50% of the tested intakes hurt the performance of the car without a tune. That's enough for me not to just throw an intake on and hope it doesn't lean me out.

Running lean and hurting performance are two different things. I don't think you quite understand the data in that test. Every intake made power. 2 of the 3 leaned out the car by .3 AFR. Thats nothing considering the stock ECU runs around a 10:1 AFR in openloop at WOT. I tune my own car to target 11.25:1 AFR in openloop. Guess what every single ECU retune does? It leans out the Openloop fueling. The problem is not all intakes are designed the same and when you run them with other mods with no em or verifying the AFR you run into trouble. Obviously the Injen intake would have caused issues in openloop fueling with no tune but the other two would have been fine.